NAME

tethereal - Dump and analyze network traffic

SYNOPSYS

tethereal [ -a capture autostop condition ] ... [ -b number of ring buffer files [:duration] ] [ -c count ] [ -d <layer type==<selector>,<decode-as protocol> ]> [ -D ] [ -f capture filter expression ] [ -F file format ] [ -h ] [ -i interface ] [ -l ] [ -L ] [ -n ] [ -N resolving flags ] [ -o preference setting ] ... [ -p ] [ -q ] [ -r infile ] [ -R display filter expression ] [ -s snaplen ] [ -S ] [ -t time stamp format ] [ -T pdml|psml|ps|text ] [ -v ] [ -V ] [ -w savefile ] [ -x ] [ -y link type ] [ -z statistics-string ] [ filter expression ]

DESCRIPTION

Tethereal is a network protocol analyzer. It lets you capture packet data from a live network, or read packets from a previously saved capture file, either printing a decoded form of those packets to the standard output or writing the packets to a file. Tethereal's native capture file format is libpcap format, which is also the format used by tcpdump and various other tools.

Ethereal can read / import the following file formats:

There is no need to tell Tethereal what type of file you are reading; it will determine the file type by itself. Tethereal is also capable of reading any of these file formats if they are compressed using gzip. Tethereal recognizes this directly from the file; the '.gz' extension is not required for this purpose.

If the -w flag is not specified, Tethereal prints a decoded form of the packets it captures or reads; otherwise, it writes those packets to the file specified by that flag.

When printing a decoded form of packets, Tethereal prints, by default, a summary line containing the fields specified by the preferences file (which are also the fields displayed in the packet list pane in Ethereal), although if it's printing packets as it captures them, rather than printing packets from a saved capture file, it won't print the ``frame number'' field. If the -V flag is specified, it prints instead a view of the details of the packet, showing all the fields of all protocols in the packet.

When writing packets to a file, Tethereal, by default, writes the file in libpcap format, and writes all of the packets it sees to the output file. The -F flag can be used to specify the format in which to write the file. The following output formats are supported:

This list is also displayed by the -h flag.

Read filters in Tethereal, which allow you to select which packets are to be decoded or written to a file, are very powerful; more fields are filterable in Tethereal than in other protocol analyzers, and the syntax you can use to create your filters is richer. As Tethereal progresses, expect more and more protocol fields to be allowed in read filters.

Packet capturing is performed with the pcap library. The capture filter syntax follows the rules of the pcap library. This syntax is different from the read filter syntax. A read filter can also be specified when capturing, and only packets that pass the read filter will be displayed or saved to the output file; note, however, that capture filters are much more efficient than read filters, and it may be more difficult for Tethereal to keep up with a busy network if a read filter is specified for a live capture.

Compressed file support uses (and therefore requires) the zlib library. If the zlib library is not present, Tethereal will compile, but will be unable to read compressed files.

A capture or read filter can either be specified with the -f or -R option, respectively, in which case the entire filter expression must be specified as a single argument (which means that if it contains spaces, it must be quoted), or can be specified with command-line arguments after the option arguments, in which case all the arguments after the filter arguments are treated as a filter expression. Capture filters are supported only when doing a live capture; read filters are supported when doing a live capture and when reading a capture file, but require Tethereal to do more work when filtering, so you might be more likely to lose packets under heavy load if you're using a read filter. If the filter is specified with command-line arguments after the option arguments, it's a capture filter if a capture is being done (i.e., if no -r flag was specified) and a read filter if a capture file is being read (i.e., if a -r flag was specified).

OPTIONS

-a
Specify a criterion that specifies when Tethereal is to stop writing to a capture file. The criterion is of the form test:value, where test is one of:

duration
Stop writing to a capture file after value seconds have elapsed.

filesize
Stop writing to a capture file after it reaches a size of value kilobytes (where a kilobyte is 1000 bytes, not 1024 bytes).

-b
If a maximum capture file size was specified, cause Tethereal to run in ``ring buffer'' mode, with the specified number of files. In ``ring buffer'' mode, Tethereal will write to several capture files. Their name is based on the number of the file and on the creation date and time.

When the first capture file fills up, Tethereal will switch to writing to the next file, until it fills up the last file, at which point it'll discard the data in the first file (unless 0 is specified, in which case, the number of files is unlimited) and start writing to that file and so on.

If the optional duration is specified, Tethereal will switch also to the next file when the specified number of seconds has elapsed even if the current file is not completely fills up.

You can only save files in libpcap format when using a ring buffer.

-c
Set the default number of packets to read when capturing live data.

-d
Specify that if the layer type in question (for example, tcp.port or udp.port for a TCP or UDP port number) has the specified selector value, packets should be dissected as the specified protocol.

Example: -d tcp.port==8888,http will decode any traffic running over TCP port 8888 as HTTP.

-D
Print a list of the interfaces on which Tethereal can capture, and exit. For each network interface, a number and an interface name, possibly followed by a text description of the interface, is printed. The interface name or the number can be supplied to the -i flag to specify an interface on which to capture.

This can be useful on systems that don't have a command to list them (e.g., Windows systems, or UNIX systems lacking ifconfig \-a); the number can be useful on Windows 2000 and later systems, where the interface name is a somewhat complex string.

Note that ``can capture'' means that Tethereal was able to open that device to do a live capture; if, on your system, a program doing a network capture must be run from an account with special privileges (for example, as root), then, if Tethereal is run with the -D flag and is not run from such an account, it will not list any interfaces.

-f
Set the capture filter expression.

-F
Set the file format of the output capture file.

-h
Print the version and options and exits.

-i
Set the name of the network interface or pipe to use for live packet capture.

Network interface names should match one of the names listed in ``tethereal -D'' (described above); a number, as reported by ``tethereal -D'', can also be used. If you're using UNIX, ``netstat -i'' or ``ifconfig -a'' might also work to list interface names, although not all versions of UNIX support the -a flag to ifconfig.

If no interface is specified, Tethereal searches the list of interfaces, choosing the first non-loopback interface if there are any non-loopback interfaces, and choosing the first loopback interface if there are no non-loopback interfaces; if there are no interfaces, Tethereal reports an error and doesn't start the capture.

Pipe names should be either the name of a FIFO (named pipe) or ``-'' to read data from the standard input. Data read from pipes must be in standard libpcap format.

-l
Flush the standard output after the information for each packet is printed. (This is not, strictly speaking, line-buffered if -V was specified; however, it is the same as line-buffered if -V wasn't specified, as only one line is printed for each packet, and, as -l is normally used when piping a live capture to a program or script, so that output for a packet shows up as soon as the packet is seen and dissected, it should work just as well as true line-buffering. We do this as a workaround for a deficiency in the Microsoft Visual C++ C library.)

This may be useful when piping the output of Tethereal to another program, as it means that the program to which the output is piped will see the dissected data for a packet as soon as Tethereal sees the packet and generates that output, rather than seeing it only when the standard output buffer containing that data fills up.

-L
List the data link types supported by the interface and exit.

-n
Disable network object name resolution (such as hostname, TCP and UDP port names).

-N
Turn on name resolving for particular types of addresses and port numbers, with name resolving for other types of addresses and port numbers turned off; the argument is a string that may contain the letters m to enable MAC address resolution, n to enable network address resolution, and t to enable transport-layer port number resolution. This overrides -n if both -N and -n are present. The letter C enables concurrent (asynchronous) DNS lookups.

-o
Set a preference value, overriding the default value and any value read from a preference file. The argument to the flag is a string of the form prefname:value, where prefname is the name of the preference (which is the same name that would appear in the preference file), and value is the value to which it should be set.

-p
Don't put the interface into promiscuous mode. Note that the interface might be in promiscuous mode for some other reason; hence, -p cannot be used to ensure that the only traffic that is captured is traffic sent to or from the machine on which Tethereal is running, broadcast traffic, and multicast traffic to addresses received by that machine.

-q
When capturing packets, don't display the continuous count of packets captured that is normally shown when saving a capture to a file; instead, just display, at the end of the capture, a count of packets captured. On systems that support the SIGINFO signal, such as various BSDs, typing your ``status'' character (typically control-T, although it might be set to ``disabled'' by default on at least some BSDs, so you'd have to explicitly set it to use it) will cause the current count to be displayed.

When reading a capture file, don't print packet information; this is useful if you're using a -z flag to calculate statistics and don't want the packet information printed, just the statistics.

-r
Read packet data from infile.

-R
Cause the specified filter (which uses the syntax of read filters, rather than that of capture filters) to be applied before printing a decoded form of packets or writing packets to a file; packets not matching the filter are discarded rather than being printed or written.

-s
Set the default snapshot length to use when capturing live data. No more than snaplen bytes of each network packet will be read into memory, or saved to disk.

-S
Decode and display packets even while writing to file.

-t
Set the format of the packet timestamp printed in summary lines. The format can be one of 'r' (relative), 'a' (absolute), 'ad' (absolute with date), or 'd' (delta). The relative time is the time elapsed between the first packet and the current packet. The absolute time is the actual time the packet was captured, with no date displayed; the absolute date and time is the actual time and date the packet was captured. The delta time is the time since the previous packet was captured. The default is relative.

-T
Set the format of the output when viewing packet data. The options are:

pdml
Packet Details Markup Language, an XML-based format for the details of a decoded packet. This information is equivalent to the packet details printed with the -V flag.

psml
Packet Summary Markup Language, an XML-based format for the summary information of a decoded packet. This information is equivalent to the information shown in the one-line summary printed by default.

ps
PostScript for a human-readable one-line summary of each of the packets, or a multi-line view of the details of each of the packets, depending on whether the -V flag was specified.

text
Text of a human-readable one-line summary of each of the packets, or a multi-line view of the details of each of the packets, depending on whether the -V flag was specified. This is the default.

-v
Print the version and exit.

-V
Cause Tethereal to print a view of the details of the packet rather than a one-line summary of the packet.

-w
Write packet data to savefile or to the standard output if savefile is ``-''.

-x
Cause Tethereal to print a hex and ASCII dump of the packet data after printing the summary or details.

-y
Set the data link type to use while capturing packets. The values reported by -L are the values that can be used.

-z
Get Tethereal to collect various types of statistics and display the result after finishing reading the capture file. Use the -q flag if you're reading a capture file and only want the statistics printed, not any per-packet information.

Note that the -z proto option is different - it doesn't cause statistics to be gathered and printed when the capture is complete, it modifies the regular packet summary output to include the values of fields specified with the option. Therefore you must not use the -q option, as that option would suppress the printing of the regular packet summary output, and must also not use the -V option, as that would cause packet detail information rather than packet summary information to be printed.

Currently implemented statistics are:

-z dcerpc,rtt,uuid,major.minor[,filter]

Collect call/reply RTT data for DCERPC interface uuid, version major.minor. Data collected is number of calls for each procedure, MinRTT, MaxRTT and AvgRTT. Example: use -z dcerpc,rtt,12345778-1234-abcd-ef00-0123456789ac,1.0 to collect data for CIFS SAMR Interface. This option can be used multiple times on the command line.

If the optional filterstring is provided, the stats will only be calculated on those calls that match that filter. Example: use -z dcerpc,rtt,12345778-1234-abcd-ef00-0123456789ac,1.0,ip.addr==1.2.3.4 to collect SAMR RTT statistics for a specific host.

-z io,phs[,filter]

Create Protocol Hierarchy Statistics listing both number of packets and bytes. If no filter is specified the statistics will be calculated for all packets. If a filters is specified statistics will be only calculated for those packets that match the filter.

This option can be used multiple times on the command line.

-z io,stat,interval[,filter][,filter][,filter]...

Collect packet/bytes statistics for the capture in intervals of interval seconds. Intervals can be specified either as whole or fractional seconds. Interval can be specified in ms resolution.

If no filter is specified the statistics will be calculated for all packets. If one or more filters are specified statistics will be calculated for all filters and presented with one column of statistics for each filter.

This option can be used multiple times on the command line.

Example: -z io,stat,1,ip.addr==1.2.3.4 to generate 1 second statistics for all traffic to/from host 1.2.3.4.

Example: -z ``io,stat,0.001,smb&&ip.addr==1.2.3.4'' to generate 1ms statistics for all SMB packets to/from host 1.2.3.4.

The examples above all use the standard syntax for generating statistics which only calculates the number of packets and bytes in each interval.

io,stat can also do much more statistics and calculate COUNT(), SUM(), MIN(), MAX(), and AVG() using a slightly different filter syntax:

  [COUNT|SUM|MIN|MAX|AVG](<field>)<filter>

One important thing to note here is that the field that the calculation is based on MUST also be part of the filter string or else the calculation will fail.

So: -z io,stat,0.010,AVG(smb.time) does not work. Use -z io,stat,0.010,AVG(smb.time)smb.time instead. Also be aware that a field can exist multiple times inside the same packet and will then be counted multiple times in those packets.

COUNT(<field>) can be used on any type which has a display filter name. It will count how many times this particular field is encountered in the filtered packet list.

Example: -z io,stat,0.010,COUNT(smb.sid)smb.sid This will count the total number of SIDs seen in each 10ms interval.

SUM(<field>) can only be used on named fields of integer type. This will sum together every occurence of this fields value for each interval.

Example: -z io,stat,0.010,SUM(frame.pkt_len)frame.pkt_len This will report the total number of bytes seen in all the packets within an interval.

MIN/MAX/AVG(<field>) can only be used on named fields that are either integers or relative time fields. This will calculate maximum/minimum or average seen in each interval. If the field is a relative time field the output will be presented in seconds and three digits after the decimal point. The resolution for time calculations is 1ms and anything smaller will be truncated.

Example: -z ``io,stat,0.010,smb.time&&ip.addr==1.1.1.1,MIN(smb.time)smb.time&&ip.addr==1.1.1.1,MAX(smb.time)smb.time&&ip.addr==1.1.1.1,MAX(smb.time)smb.time&&ip.addr==1.1.1.1''

This will calculate statistics for all smb response times we see to/from host 1.1.1.1 in 10ms intervals. The output will be displayed in 4 columns; number of packets/bytes, minimum response time, maximum response time and average response time.

-z conv,type[,filter]

Create a table that lists all conversations that could be seen in the capture. type specifies which type of conversation we want to generate the statistics for; currently the supported ones are

  "eth"   Ethernet
  "fc"    Fibre Channel
  "fddi"  FDDI
  "ip"    IP addresses
  "ipx"   IPX addresses
  "tcp"   TCP/IP socket pairs  Both IPv4 and IPv6 are supported
  "tr"    Token Ring
  "udp"   UDP/IP socket pairs  Both IPv4 and IPv6 are supported

If the optional filter string is specified, only those packets that match the filter will be used in the calculations.

The table is presented with one line for each conversation and displays number of packets/bytes in each direction as well as total number of packets/bytes. The table is sorted according to total number of bytes.

-z proto,colinfo,filter,field

Append all field values for the packet to the Info column of the one-line summary output. This feature can be used to append arbitrary fields to the Info column in addition to the normal content of that column. field is the display-filter name of a field which value should be placed in the Info column. filter is a filter string that controls for which packets the field value will be presented in the info column. field will only be presented in the Info column for the packets which match filter.

NOTE: In order for Tethereal to be able to extract the field value from the packet, field MUST be part of the filter string. If not, Tethereal will not be able to extract its value.

For a simple example to add the ``nfs.fh.hash'' field to the Info column for all packets containing the ``nfs.fh.hash'' field, use

-z proto,colinfo,nfs.fh.hash,nfs.fh.hash

To put ``nfs.fh.hash'' in the Info column but only for packets coming from host 1.2.3.4 use:

-z ``proto,colinfo,nfs.fh.hash && ip.src==1.2.3.4,nfs.fh.hash''

This option can be used multiple times on the command line.

-z rpc,rtt,program,version[,filter]

Collect call/reply RTT data for program/version. Data collected is number of calls for each procedure, MinRTT, MaxRTT and AvgRTT. Example: use -z rpc,rtt,100003,3 to collect data for NFS v3. This option can be used multiple times on the command line.

If the optional filterstring is provided, the stats will only be calculated on those calls that match that filter. Example: use -z rpc,rtt,100003,3,nfs.fh.hash==0x12345678 to collect NFS v3 RTT statistics for a specific file.

-z rpc,programs

Collect call/reply RTT data for all known ONC-RPC programs/versions. Data collected is number of calls for each protocol/version, MinRTT, MaxRTT and AvgRTT. This option can only be used once on the command line.

-z smb,rtt[,filter]

Collect call/reply RTT data for SMB. Data collected is number of calls for each SMB command, MinRTT, MaxRTT and AvgRTT. Example: use -z smb,rtt. The data will be presented as separate tables for all normal SMB commands, all Transaction2 commands and all NT Transaction commands. Only those commands that are seen in the capture will have its stats displayed. Only the first command in a xAndX command chain will be used in the calculation. So for common SessionSetupAndX + TreeConnectAndX chains, only the SessionSetupAndX call will be used in the statistics. This is a flaw that might be fixed in the future.

This option can be used multiple times on the command line.

If the optional filterstring is provided, the stats will only be calculated on those calls that match that filter. Example: use -z ``smb,rtt,ip.addr==1.2.3.4'' to only collect stats for SMB packets echanged by the host at IP address 1.2.3.4 .

-z smb,sids

When this feature is used Tethereal will print a report with all the discovered SID and account name mappings. Only those SIDs where the account name is known will be presented in the table.

For this feature to work you will need to either to enable ``Edit/Preferences/Protocols/SMB/Snoop SID to name mappings'' in the preferences or you can override the preferences by specifying -o ``smb.sid_name_snooping:TRUE'' on the Tethereal command line.

The current methods used by Tethereal to find the SID->name mapping is relatively restricted but is hoped to be expanded in the future.

-z mgcp,rtd[,filter]

Collect requests/response RTD (Response Time Delay) data for MGCP. This is similar to -z smb,rtt). Data collected is number of calls for each known MGCP Type, MinRTD, MaxRTD and AvgRTD. Additionally you get the number of duplicate requests/responses, unresponded requests, responses ,which don't match with any request. Example: use -z mgcp,rtd.

This option can be used multiple times on the command line.

If the optional filterstring is provided, the stats will only be calculated on those calls that match that filter. Example: use -z ``mgcp,rtd,ip.addr==1.2.3.4'' to only collect stats for MGCP packets exchanged by the host at IP address 1.2.3.4 .

-z h225,counter[,filter]

Count ITU-T H.225 messages and their reasons. In the first column you get a list of H.225 messages and H.225 message reasons, which occur in the current capture file. The number of occurences of each message or reason is displayed in the second column.

Example: use -z h225,counter.

This option can be used multiple times on the command line.

If the optional filterstring is provided, the stats will only be calculated on those calls that match that filter. Example: use -z ``h225,counter,ip.addr==1.2.3.4'' to only collect stats for H.225 packets exchanged by the host at IP address 1.2.3.4 .

-z h225,srt[,filter]

Collect requests/response SRT (Service Response Time) data for ITU-T H.225 RAS. Data collected is number of calls of each ITU-T H.225 RAS Message Type, Minimum SRT, Maximum SRT, Average SRT, Minimum in Frame, and Maximum in Frame. You will also get the number of Open Requests (Unresponded Requests), Discarded Responses (Responses without matching request) and Duplicate Messages. Example: use -z h225,srt.

This option can be used multiple times on the command line.

If the optional filterstring is provided, the stats will only be calculated on those calls that match that filter. Example: use -z ``h225,srt,ip.addr==1.2.3.4'' to only collect stats for ITU-T H.225 RAS packets exchanged by the host at IP address 1.2.3.4 .

-z sip,stat[,filter]

This option will activate a counter for SIP messages. You will get the number of occurences of each SIP Method and of each SIP Status-Code. Additionally you also get the number of resent SIP Messages (only for SIP over UDP).

Example: use -z sip,stat.

This option can be used multiple times on the command line.

If the optional filter string is provided, the stats will only be calculated on those calls that match that filter. Example: use -z ``sip,stat,ip.addr==1.2.3.4'' to only collect stats for SIP packets exchanged by the host at IP address 1.2.3.4 .

CAPTURE FILTER SYNTAX

See manual page of tcpdump(8).

READ FILTER SYNTAX

For a complete table of protocol and protocol fields that are filterable in Tethereal see ethereal-filter(4).

FILES

The ethereal.conf file, which is installed in the etc directory under the main installation directory (for example, /usr/local/etc) on UNIX-compatible systems, and in the main installation directory (for example, C:\Program Files\Ethereal) on Windows systems, and the personal preferences file, which is $HOME/.ethereal/preferences on UNIX-compatible systems and %APPDATA%\Ethereal\preferences (or, if %APPDATA% isn't defined, %USERPROFILE%\Application Data\Ethereal\preferences) on Windows systems, contain system-wide and personal preference settings, respectively. The file contains preference settings of the form prefname:value, one per line, where prefname is the name of the preference (which is the same name that would appear in the preference file), and value is the value to which it should be set; white space is allowed between : and value. A preference setting can be continued on subsequent lines by indenting the continuation lines with white space. A # character starts a comment that runs to the end of the line.

The system-wide preference file is read first, if it exists, overriding Tethereal's default values; the personal preferences file is then read, if it exists, overriding default values and values read from the system-wide preference file.

The disabled protocols file, which is $HOME/.ethereal/disabled_protos on UNIX-compatible systems and %APPDATA%\Ethereal\disabled_protos (or, if %APPDATA% isn't defined, %USERPROFILE%\Application Data\Ethereal\disabled_protos) on Windows systems, contain a list of protocols that have been disabled, so that their dissectors are never called. The file contains protocol names, one per line, where the protocol name is the same name that would be used in a display filter for the protocol. A # character starts a comment that runs to the end of the line.

The ethers file, which is found in the /etc directory on UNIX-compatible systems, and in the main installation directory (for example, C:\Program Files\Ethereal) on Windows systems, is consulted to correlate 6-byte hardware addresses to names. If an address is not found in the ethers file, the $HOME/.ethereal/ethers file on UNIX-compatible systems, and the %APPDATA%\Ethereal\ethers file (or, if %APPDATA% isn't defined, the %USERPROFILE%\Application Data\Ethereal\ethers file) on Windows systems is consulted next. Each line contains one hardware address and name, separated by whitespace. The digits of the hardware address are separated by either a colon (:), a dash (-), or a period (.). The following three lines are valid lines of an ethers file:

  ff:ff:ff:ff:ff:ff          Broadcast
  c0-00-ff-ff-ff-ff          TR_broadcast
  00.00.00.00.00.00          Zero_broadcast

The manuf file, which is installed in the etc directory under the main installation directory (for example, /usr/local/etc) on UNIX-compatible systems, and in the main installation directory (for example, C:\Program Files\Ethereal) on Windows systems, matches the 3-byte vendor portion of a 6-byte hardware address with the manufacturer's name; it can also contain well-known MAC addresses and address ranges specified with a netmask. The format of the file is the same as the ethers file, except that entries of the form

  00:00:0C      Cisco

can be provided, with the 3-byte OUI and the name for a vendor, and entries of the form

  00-00-0C-07-AC/40     All-HSRP-routers

can be specified, with a MAC address and a mask indicating how many bits of the address must match. Trailing zero bytes can be omitted from address ranges. That entry, for example, will match addresses from 00-00-0C-07-AC-00 through 00-00-0C-07-AC-FF. The mask need not be a multiple of 8.

The ipxnets file, which is found in the /etc directory on UNIX-compatible systems, and in the main installation directory (for example, C:\Program Files\Ethereal) on Windows systems, correlates 4-byte IPX network numbers to names. If a network number is not found in the ipxnets file, the $HOME/.ethereal/ipxnets file on UNIX-compatible systems, and the %APPDATA%\Ethereal\ipxnets file (or, if %APPDATA% isn't defined, the %USERPROFILE%\Application Data\Ethereal\ipxnets file) on Windows systems, is consulted next. The format is the same as the ethers file, except that each address if four bytes instead of six. Additionally, the address can be represented a single hexadecimal number, as is more common in the IPX world, rather than four hex octets. For example, these four lines are valid lines of an ipxnets file.

  C0.A8.2C.00              HR
  c0-a8-1c-00              CEO
  00:00:BE:EF              IT_Server1
  110f                     FileServer3

SEE ALSO

ethereal-filter(4) ethereal(1), editcap(1), tcpdump(8), pcap(3)

NOTES

Tethereal is part of the Ethereal distribution. The latest version of Ethereal can be found at http://www.ethereal.com.

AUTHORS

Tethereal uses the same packet dissection code that Ethereal does, as well as using many other modules from Ethereal; see the list of authors in the Ethereal man page for a list of authors of that code.